Various organic solvents have been used as cleaning liquids for the removal of contaminants from contaminated articles and materials. Certain fluorine-containing organic compounds, such as 1,1,2-trichloro-1,2,2-trifluoroethane, are useful for this purpose, particularly with regard to cleaning organic polymers and plastics which may be sensitive to other more common and more powerful solvents such as trichloroethylene or perchloroethylene. Recently, however, there have been efforts to reduce the use of certain compounds such as trichlorotrifluoroethane (which contain chlorine) because of a concern over their potential to deplete ozone, and to affect thereby the layer of ozone that is considered important in protecting the Earth's surface from ultraviolet radiation.
Boiling point, flammability, and solvent power can often be adjusted by preparing mixtures of solvents. For example, certain mixtures of 1,1,2-trichloro-1,2,2-trifluoroethane with other solvents (e.g., isopropyl alcohol and nitromethane) have been reported as useful in removing contaminants that are not removed by 1,1,2-trichloro-1,2,2-trifluoroethane alone, and in cleaning articles, such as electronic circuit boards, where the requirements for a cleaning solvent are relatively stringent (i.e., it is generally desirable in circuit board cleaning to use solvents that have low boiling points, are non-flammable, have low toxicity, and have high solvent power so that flux (such as rosin) and flux residues which result from soldering electronic components to the circuit board, can be removed without damage to the circuit board substrate).
Whereas boiling point, flammability, and solvent power can often be adjusted by preparing mixtures of solvents, the utility of the resulting mixtures can be enhanced for certain applications if the mixtures do not fractionate to an undesirable degree during use and recovery or reuse. Azeotropic compositions, with their constant boiling points and constant composition characteristics, are thus considered particularly useful.
A number of compositions using halohydrocarbons containing fluorine have been discovered and in some cases used as solvents for the removal of solder fluxes and flux residues from printed circuit boards and for miscellaneous vapor degreasing applications. For example, U.S. Pat. No. 2,999,815 discloses the azeotrope of 1,1,2-trichloro-1,2,2-trifluoroethane with acetone; U.S. Pat. No. 3,903,009 discloses a ternary azeotrope of 1,1,2-trichloro-1,2,2-trifluoroethane with nitromethane and ethanol; U.S. Pat. No. 3,573,213discloses an azeotrope of 1,1,2-trichloro-1,2,2-trifluoroethane with nitromethane; U.S. Pat. No. 3,789,006 discloses the ternary azeotrope of 1,1,2-trichloro-1,2,2-trifluoroethane with nitromethane and isopropyl alcohol; U.S. Pat. No. 3,728,268 discloses the ternary azeotrope of 1,1,2-trichloro-1,2,2-trifluoroethane with acetone and ethanol; U.S. Pat. No. 2,999,817 discloses the binary azeotrope of 1,1,2 -trichloro-1,2,2-trifluoroethane and methylene chloride; and U.S. Pat. No. 4,715,900 discloses ternary compositions of trichlorotrifluoroethane, dichlorodifluoroethane, and ethanol or methanol.
As noted above, many solvent compositions which have proven useful for cleaning contain at least one component that is a halogen-substituted hydrocarbon containing chlorine, and concerns have been raised over the ozone depletion potential of halogen-substituted hydrocarbons that contain chlorine. Efforts are being made to develop compositions that may at least partially replace the chlorine-containing components with other components having lower potential for ozone depletion.
Various methods of preparing organic compounds containing fluorine are known. The fluorination of double bonds with elemental fluorine has been discussed in S. Rozen, et al., J. Org. Chem., 51, 3607 (1986); L. Conte, et al., J. Fluorine Chem., 38, 319 (1988); and C. Gervasutti, et al., U.S. Pat. No. 4,754,085 (1988).